Laminates of films and methods and apparatus for the manufacture

ABSTRACT

A laminate of thermoplastic polymeric films comprises a fluted ply A and non-fluted ply B, adhered to one another in bonded zones along some of the flute crests the fluted ply A. The wavelength of the flutes is preferably no more than 3 mm. Ply A has a generally uniform thickness or can have attenuated zones of lessor thickness extending parallel to the flute direction, each bonded zone being located mainly within an attenuated zone. The flutes can be sinuous with crests on both sides of ply A and can be adhered on each side to a ply B. The flutes can be filled with filler material, including reinforcement strands, and one or both sides can be perforated. The method and apparatus employ aligned grooved fluting rollers and a grooved laminating roller.

The present invention relates to a flexible laminate of films fromthermoplastic polymer material for applications in which relatively highyield strength and ultimate tensile strength is required, and a methodand apparatus for its manufacture.

Examples of such applications are: tarpaulins, pondliners, substitute ofgeotextiles, weather protective laminates, greenhouse film, industrialbags, carrier bags and self-standing pouches.

For economical reasons there is an increasing need to reduce thethickness or square metre weight of flexible film made fromthermoplastic polymer material. The limits are partly set by therequired strength properties, and partly by the required self supportingcapability, i.e. stiffness with respect to banding. These needs havemainly been met by selected developments of the thermoplastic polymercompositions and as far as the strength is concerned also by biaxialorientation, or by cross-lamination of films each of which exhibits agenerally monaxial or unbalanced biaxial orientation.

From strength point of view essential savings can be achieved by suchorientation and/or cross-lamination processes.

Thus as an example an industrial bag made from extruded polyethylenefilm of the best suited grades and destined for packing of 25 kgpolyethylene granules must generally have a thickness of 0.12–0.15 mm inorder to satisfy the normal strength requirements, while this thicknesscan be brought down to about 0.07 mm by use of optimized oriented andcross-laminated film from polyethylene. However, when thiscross-laminate is made in the known manner, few available types ofmachines for manufacturing bags from film, and few available types ofmachines for filling the bags, can work adequately with film which is sothin and flimsy.

A cross-laminate which, besides the improved strength propertiesobtained by the orientation and cross-lamination also by virtue of itsgeometrical structure shows significant improvements in this respect, isdescribed in the inventor's earlier Specification EP-A-0624126.

This is a cross-laminate of a slightly waved configuration in which thematerial of the curved crests on one or both sides of the laminate isthicker than elsewhere, the material between these thicker curved crestsbeing generally straightened out. (See FIGS. 1 and 2 of said patentpublications.) The structure is obtained by stretching between severalsets of grooved rollers under special conditions. This stretching alsoimparts transverse orientation. The disclosed wavelengths of the finalproducts are between 2.2 and 3.1 mm.

Cross-laminates according to the said patent have been producedindustrially since 1995 for manufacture of industrial bags fromcombinations of high molecular weight high density polyethylene(HMWHDPE) and linear low density polyethylene (LLDPE) with film weightabout 90 gm⁻², and the slightly waved shape in combination with thethickened crests imparts a stiffness in one direction of the film whichhas proven to be very important for the performance of the bag machineswith such relatively thin film. However, the film is not adequate forwork with the 70 gm⁻² gauge which satisfies the strength requirements.

Furthermore the corrugated character of the film surface makes aparticularly fine print (as often required) impossible and also to someextent reduces the friction between filled bags in a stack, when thelayers of this stack are built up with the bags in crisscrossingarrangement as usually done.

As another example an agricultural tarpaulin (e.g. for protection ofcrops) made from a 70 gm⁻² cross-laminate of oriented polyethylene filmswould be a fully adequate substitute of a 100 gm⁻² tarpaulin made fromextrusion-coated woven tape, if only objective criteria were applied.However, in actual fact the average customer to agricultural tarpaulinsmakes his choice to a great extent on the basis of the “handle” and theappearance, and will reject the 70 gm⁻² tarpaulin due to its flimsiness,judging that it lacks substance.

The stiffness can of course always be increased by suitableincorporation of a filler, (and the present invention includes that asan additional option) but this will always more or less be at theexpense of puncture and tear propagation resistance, especially underimpact actions.

Object of the present invention is to add a “feel of substance” andimprove stiffness in laminates of films at least in one direction,without sacrificing the laminate's character of feeling and looking likea generally two-dimensional structure, furthermore without essentiallyharming the puncture and tear propagation resistance, and when desiredalso providing a good printability at least on one side of the laminate.

The basic idea behind the present invention is to apply the corrugatedpaperboard principle to laminates of thermoplastic films, but in such away that the flute structure is made extraordinarily fine(“minifluted”), so as to obtain a laminate which, in spite of thestructurally increased stiffness (at least in one direction), can stillsatisfy the above-mentioned conditions.

In itself the application of the corrugated paperboard principle to thethermoplastic film is not new, but the finest flute structure which hasbeen disclosed in patent literature, namely in U.S. Pat. No. 4,132,581col. 6, ln. 66, is 50+/−3 flutes per foot corresponding to a wavelengthof about 6.0 mm. It must also strongly be doubted that a wavelengthlower than this can be achieved by the method disclosed in the saidpatent, in which the first bonding process takes place under use of arow of many sealer bars supported and transported by a belt.

The sealer bars are transverse to the direction of movement (the machinedirection) so the fluting also becomes perpendicular to this direction.

The use of the method of the said U.S. patent is stated to bemanufacture of board material, and the thickness of the fluted ply isindicated to be about 0.004–0.025 inches (0.10–0.625 mm). In the exampleit is 0.018 inches (0.45 mm). Other patents dealing with the use of thecorrugated paperboard principle to thermoplastic film for the making ofpanels or boards are U.S. Pat. No. 3,682,736, U.S. Pat. No. 3,833,440,U.S. Pat. No. 3,837,973, EP-A-0325780 and WO-A-94/05498.

Japanese Patent Application Hei 02-052732 discloses laminates consistingof a corrugated thermoplastic film bonded to a flat thermoplastic film,which on its other side is bonded to paper. (The paper and flat sheetare first joined and then the corrugated film is added.) The flutes,which also in this case are perpendicular to the machine direction arepressed flat and adhesively closed at intervals so that a large numberof airtight vesicles are formed. The stated use of this product is forcushion material, sound insulating material, heat- andmoisture-insulating material and wall decorative material. The thicknessof the corrugated sheet and flat sheet are not indicated, neither arethe wavelength of the fluting and the length of the vesicles, but it ismentioned that the dimensions can be selected depending on the use ofthe laminate. However, it must be understood as implied that thewavelength in any case will be no lower than the lowest mentioned in theabove-mentioned U.S. Pat. No. 4,132,581 (i.e. about 6 mm). One reasonfor judging this is that this would not be advantageous for thementioned purposes, except for decoration, while another reason is thatthe disclosed apparatus would not be able to work with a lowerwavelength (i.e. a lower pitch of the gear rollers) except for making anextremely shallow and practically useless fluting. This is due to thefact that thermoplastic film is resilient and not permanently formableat ambient temperature which as implied by the presentation in thedrawing is used in the said method. If the pitch is low on the gearrollers which produce the fluting and the lamination, the corrugatedfilm will “jump out” of the grooves in the forming and laminating rollerduring its passage from the location where forming of flutes takes placeto the location where bonding takes place. The patent publication doesnot mention any means to hold the flutes in shape in the grooves of theroller.

In a conventional corrugator for manufacture of corrugated paperboardthere are provided tracks or shield to hold the fluted paper in thegrooves. At ambient temperature this allows the paper to be more readilypermanently formed.

Similar tracks or shields in unmodified form cannot be used withthermoplastic film under production conditions since friction againstthe track or shield quickly would create congestion by heating of thepolymer.

An improved, frictionless way of holding of flutes of paper in thegrooves of a roller is known from U.S. Pat. No. 6,139,938, namely bymaintaining a controlled under pressure within the grooves (see FIGS. 9and 10 and col. 7 lines 25–34). This U.S. patent deals entirely withcorrugated paper laminates having particularly low wavelength whilemanufacture of corrugated structures from thermoplastic films is notmentioned. However, the improved method of holding the flutes will infact also, depending on the film thickness, be applicable to fine flutesin thermoplastic film. This was found in connection with the developmentof the present invention. However as mentioned above, the Japanesepatent application does not disclose any precautions to hold the flutesin shape in the grooves.

The development of the particularly fine flute structure, the“miniflutes”, which is the object of the present invention has made thecorrugated paperboard principle applicable to completely differentfields of use such as the fields mentioned at the very beginning of thisspecification.

This has comprised a development of new types of machinery based ongrooved rollers with a very fine pitch. As it will appear from theexample the wavelength in a 90 gm⁻² “minifluted” 2-ply laminate (eachply about 45 gm⁻²) has in actual fact been brought down to 1.0 mmthrough a process which can be carried out industrially, and aftershrinkage of the flat ply transversely to the flutes it has even beenbrought down to 0.8 mm. Especially by further use of shrinkage it canprobably be brought further down e.g. to about 0.5 mm. The mentioned2×45 gm⁻² corresponds to an average thickness of about 0.074 mm (2×0.037mm) if the laminate were pressed flat.

The invention is not limited to pressed-flat thicknesses around thisvalue, but also comprises, very generally speaking, minifluted laminatesof an average thickness in compacted form which is roughly about 0.3 mmor lower. Thicknesses down to 0.03 mm or even lower can be made forspecial purposes.

Nor is the invention limited to the use in connection withcross-laminates of oriented films. For different purposes differentcombinations of strength properties are required. Cross-laminates can,as is known, be produced with suitable combinations of severalcategories of strength properties but for many purposes other types ofstrength laminates may be preferable when the cost of the manufacturingprocess also is considered, and the present invention can also be usefulin such other strength laminates as it further shall be specified below.

By making the wavelength as low as 3 mm or less, the laminate loses itscharacter of being a board material and gets appearance, handle andbending properties like a flexible film (see the example). It also getsimproved puncture properties, compared to laminates made from similarplies but with longer wavelength, since in the latter there is a largetendency for the plies to be ruptured individually instead ofcooperating in the resistance against the puncture.

The “minifluted” laminate also has the advantage that it can receive afine print on the flat side and a coarse print on the corrugated side.

Compared to non-corrugated laminates of the same composition and samesquare metre weight it feels much more substantial due to the increasedstiffness in one direction and due to the increased-volume.

In the case of cross-laminates it is well-known that a weak bondingbetween the plies, or strong bonding or line-bonding, gives muchimproved tear propagation resistance, since it allows the tear toproceed in different directions in the different plies. Thereby thenotch effect is reduced. Since a cross-laminate with one ply corrugatedwill be line-bonded, it will show improved tear propagation resistance,no matter whether the wavelength is short or long, however“mini-fluting” makes the tear stop after a very short propagation, whichof course is very advantageous in most cases.

For the sake of good order, it should be mentioned that there alreadyhave been described “minifluted” laminates in literature, howeverlaminates of which at least the fluted ply consists of a material whichis not a thermoplastic film or an assembly of thermoplastic films.

Thus U.S. Pat. No. 6,139,938, which has been mentioned above, has forits object a 3-ply paper laminate with a corrugated paper sheet in themiddle and flat paper sheets on each side, like normal corrugated paperboard, however claimed to comprise 500–600 flutes per metrecorresponding to a wavelength of 1.67–2.00 mm. This state purpose is toimprove the printability.

Japanese patent publication No. 07-251004 relates to an absorbingproduct in which a plane thermoplastic synthetic fiber sheet isthermally bonded to a corrugated sheet mainly consisting of activecarbon fibers. The wavelength of the corrugation is 2.5–20 mm.

Japanese patent publication No. 08-299385 relates to an absorbentlaminate consisting of a fluted non-woven fabric bonded on one side to aplane sheet or film, which can be a thermoplastic film. Between thesetwo plies there is nested a water-absorbing material. The wavelength isclaimed to be 3–50 mm, and it is stated that there would not besufficient space for the absorbing material if it were less. The productis for diapers and the similar products.

More precisely expressed the present invention concerns a laminatecomprising at least a monofilm-formed or multifilm-formed ply (A) andanother monofilm-formed or multifilm-form ply (B) both mainly consistingof thermoplastic polymer material, whereby at least A consists ofcold-orientable material in which A has a waved flute configurationwhile B is not waved, and B on a first side is adhesively bonded inbonding zones to the crests on a first side of A. A characterisingfeature of the laminate is that the wavelength of the said configurationis no more than 3 mm. The use of cold-orientable material in A isimportant for the strength of the product. Furthermore it is normallyimportant that the adhesive bonding has been established through alamination layer, so that melting of the main portions of A and B can beavoided during the lamination process, and that either the thickness ofA generally is the same within the non-bonded zones as it is within thebonded zones, or A exhibits zones which are attenuated in the solidstate and extend parallel to the flute direction in such a manner thateach bonding zone mainly is located within one of the attenuated zones.These attenuated zones will be referred to as the “first attenuatedzones” since there also may be further attenuated zones, as it shall beexplained later.

In this connection, an essential attenuation of A in the non-bondedzones, as compared to the thickness of A in the bonded zones, will ofcourse have a negative-influence on the resistance to bending in thestiff direction (but it is generally easier to make the fluted laminateso). By contrast this resistance to bending is enhanced, seen inrelation to the average thickness of ply A, when each bonding zonemainly falls within one of these attenuated zones. The attenuated zonesalso facilitate the manufacturing process as it later shall beexplained. It is noted that while attenuation by stretching in themolten state reduces the tensile strength, attenuation by stretching insolid state increases the tensile strength in the direction in whichthis stretching has taken place.

While I here have identified the laminate as comprising the plies A andB, each “ply” can consist of one or more “films”, normally extrudedfilms, and each extruded film can and normally will consist of severalco-extruded “layers”. Thus the “lamination layer” through which thebonding takes place will normally be a co-extruded layer, however it canalso be a thin film applied in a conventional extrusion-laminationprocess.

While an upper limit of 3 mm wavelength has been chosen as a suitablevalue for distinguishing the product of the invention from corrugatedboard material, it is generally better to keep the wavelength within 2.5mm, preferably within 2 mm and more preferably 1.5 mm. As alreadymentioned and shown in the example the inventor has been able to make it1.0 mm and under use of shrinkage after lamination even 0.8 mm.

As it appears from the introduction, the use of the present invention ismainly for strength film. This needs not always mean good strength inall directions; by contrast there are cases, e.g. in construction ofbags, where the focus should be on the strength in one direction,combined with a certain puncture and tear-propagation resistance. As anexample a conventional industrial bag of film thickness 0.160 mm madefrom a blend of 90% LDPE and 10% LLDPE will typically in itslongitudinal direction show a yield force of 20 Ncm⁻¹, i.e. a yieldtension of 12.5 MPa and in its transverse direction shows a yield forceof 16 Ncm⁻¹, i.e. a yield tension of 10.0 MPa.

Cross-laminated film material in average thickness 0.086 mm forheat-sealable bags developed by the inventor and manufactured inaccordance with the above-mentioned EP-A-0624126 shows in its strongestdirection a yield force of 20 Ncm⁻¹, i.e. 23 MPa, and in its weakestdirection a yield force of 17 Ncm⁻¹, i.e. a yield tension of 20 MPa.

Since the invention in principle relates to flexible laminates for useswhere relatively high strength is required, although the emphasis of theinvention is on stiffness, feel and appearance, the yield tension of thelaminate in its strongest direction should normally be no less than 15MPa, preferably no less than 25 MPa. Correspondingly the ultimatetensile tension is conveniently about twice the said indicated values,or more. Here the cross section in mm² is based on the solid materialonly, not including the air spaces, and it is an average, consideringthat ply A may have attenuated zones.

The yield tensions mentioned here refer to tensile testing at anextension velocity of 500% per minute. They are established fromstrain/stress graphs. These graphs will begin linear accordingly toHook's law, but will normally soon deviate from linearity although thedeformation still is elastic. In principle the yield tension should bethe tension at which the deformation becomes permanent, but thiscritical value, which is velocity dependent, is practically impossibleto determine. The way yield tension normally is determined in practice,and also considered determined in connection with the present invention,is the following:

In case the tension reaches a relative maximum, then remains constant ordecreases under continued elongation, later to increase again untilbreak occurs, the relative maximum of the tension is considered to bethe yield tension. The sample may also break at this point, and then theyield tension equals the ultimate tensile tension. If however thetension continues to increase with the continued elongation, but withmuch lower increases in tension per percentage elongation, then thestrain/stress curve after yield, and after it practically has become astraight line, is extrapolated backward to intersect with the line whichrepresents the Hook's-Law-part of the stretching. The tension at theintersection between the two lines is the defined yield tension.

An embodiment of the invention is characterised in that the ply A by thechoice of polymer material or by an incorporated filler or byorientation, within the non-bonded zones exhibits an average yieldtension parallel to the direction of fluting, which when it isdetermined as explained above, is no less than 30 Nmm⁻² (cross-sectionof ply A alone), preferably no less than 50 Nmm⁻² and still morepreferably no less than 75 Nmm⁻².

As already mentioned, A is preferably solid-state-attenuated in zones(the “first attenuated zones”) and each bonding zone is mainly locatedwithin a first attenuated zone. These zones should be understood asdelimited by the positions where the thickness of A is an averagebetween A's lowest thickness within the first attenuated zone and A'shighest thickness within the adjacent non-bonded zone.

Another important embodiment of the invention is characterised in that Awithin each non-bonded zone and outside the first attenuated zone ifsuch zone is present (delimited as mentioned above) is molecularlyoriented mainly in a direction parallel to the direction of the flutesor a direction close to the latter as established by shrinkage tests.Such tests are commonly used. In this connection, a component oforientation in A perpendicular to the direction of the flutes will notcontribute to the yield tension in any direction, but will contribute tocertain other strength properties.

A preferable limitation of the extension of each first attenuationzone—preferable with a view to the stiffness in one direction—is alaminate in which said first attenuated zones are present in Acharacterized in that each such zone of attenuated A, if it extendsbeyond the corresponding zone of bonding into a non-bonded zone of A, islimited to a width which leaves more than half of and preferably no lessthan 70% of the width of the non-bonded zone, as not belonging to anyfirst attenuated zone, this width being measured along the curvedsurfaces, and the preferable thickness of these zones are specified in alaminate characterized in that said first attenuated zones of A areattenuated so that the minimum thickness in that zone is less than 75%of the maximum thickness of A in the non-bonded zone, preferably lessthan 50% and more preferably less than 30% of that maximum thickness.

Additionally to the first attenuated zones it can be very advantageousto have a second solid-state-attenuated zone (hereinafter the secondattenuated zone) between each pair of adjacent first attenuated zones.These second attenuated zones should be narrower than the firstones—preferably as narrow as possible but also alternated so that thethickness of A in the zone is as thin as possible—and located on thecrests of A on the side opposite to the bonded zones. They act as“hinges”, and if they are made narrow and deep enough they improve thestiffness since the cross-section of A becomes zig-zagging instead ofsmoothly waved (as described further in connection with FIG. 3) and Aand B thereby form triangular structures. They also essentiallyfacilitate the manufacturing process, which is explained below.

In addition to the improvements in stiffness caused by the first andsecond attenuated zones (improvements seen in relation to the averagethickness of A) each set of zones also normally improves the resistanceagainst shock actions, i.e. they normally improve impact strength,shock-puncture resistance and shock-tear-propagation resistance. This isbecause there is started a stretching (or further stretching if Aalready was stretched) and this stretching normally has a tendency toprogress under shock actions, whereby the first and second attenuatedzones can act as shock-absorbers.

Normally the wavelength of each flute including an adjacent bonding zoneshould be no longer than 50 times the highest thickness of A within theflute, preferably no more than 40 times and still more preferably nomore than 30 times the said thickness. As an example, if the highestthickness of A is 0.037 mm as in the operative example below, thementioned values correspond to wavelengths of 1.85, 1.48 and 1.11 mmrespectively.

In order to “integrate” the plies conveniently with each other in orderfor strength purposes, the width of each bonding zone should normally beno less than 15%, preferably no less that 20% and still more preferablyno less than 30% of the wavelength, and in order to achieve asubstantial effect of the fluting, the width of each non-bonded zone ofA as measured between the two adjacent bonding zones and measured alongits curved surface, should preferably be no less than 10% and preferablyno less than 20% longer than the corresponding linear distance. This isa measure of the depth of the flutes.

For many purposes, e.g., when increased stiffness against bending is alldirections is wanted, there can be a non-waved monolayered ormultilayered film C on the side of A which is opposite to B as specifiedin a laminate characterized in that it comprises a further non-wavedmonofilm formed or multifilm formed ply(C) of thermoplastic polymermaterial, C being bonded to the crests of A on the second side of thelatter through a lamination layer.

A fluted outside surface on a bag has a mentioned above a disadvantage,namely in connection with printed and stacking of the filled bag.However there are articles in which the special roughness of a flutedsurface can be very advantageous in use e.g. on mats. For such articlesthere can advantageously be two waved mono- or multilayered plies (A)and (D) laminated to the two opposing sides of the non-waved mono- ormultilayered film (b), as specified in a laminate characterised in thatit comprises a further monofilm formed or multifilm formed ply (D)consisting of thermoplastic, cold-orientable polymer material, said plyhaving waved flute configuration, the crests on one side of D beingbonded to the second side of B through a lamination layer, and thewavelength of D's flute configuration preferably being no more than 3mm.

The films A, B, C and D will normally consist of polyolefin and willnormally be produced by a process which involves extrusion. This willnormally be a co-extrusion process by which lamination layers andoptionally heat-seal layers are joined with the main body of the film.

At least some of the flutes can be flattened at longitudinally spacedintervals and preferably bonded across the entire width of each flute atthe flattened locations to make the flutes form a row of narrow closedelongated pockets. Preferably the flattened portions of a number ofmutually adjacent flutes or of all flutes form a series of linestransverse to the longitudinal direction of the flutes. This can makethe corrugated laminate look and feel more textile-like, almost make theimpression of a woven structure, and make it more flexible in thedirection which otherwise is stiff, without losing the feel of bulk andsubstance. Flattening can also be used to create preferential locationsfor bending.

Further description of different embodiments of the product and ofparticular uses will follow after the description of the method.

In accordance with the above characterization of the laminate of theinvention, the method of manufacture which takes place under the use ofa grooved roller for formation of the flutes, and also under use of agrooved roller for the lamination by heat and pressure (which in certaincase can be the same grooved roller) is characterised in that thedivision on the roller which produced the lamination is at the highest 3mm. The new method according to the invention is a method ofmanufacturing a laminate or monofilm formed or multifllm formed ply (A)with another monofilm formed or multifilm formed ply (B) both consistingof thermoplastic polymer material in which A has a waved fluteconfiguration while B is not waved, and B on a first side is adhesivelybonded in zones to the crests on a first side of A, in which further thewaved flute structure is formed by the use of a grooved roller, and thesaid bonding with B is carried out under heat and pressure and alsounder use of a grooved roller, and at least A is selected as mainlyconsisting of solid-state orientable material, characterised in that thedivision on the grooved roller which produces the lamination on the saidcrests is at the highest 3 mm.

New apparatus for carrying out the method is is an apparatus for forminga laminate comprising feeding means for feeding a continuous web of plyB formed of a thermoplastic material from a supply to a laminatingstation; a grooved fluting roller for imposing a waved fluted structureon a ply of thermoplastic material; feeding means for feeding acontinuos web of ply A formed of a thermoplastic material from a supplyto the grooved fluting roller and thereafter to the laminating stationin face to face relationship with ply B; wherein the laminating stationcomprises a grooved laminating roller which is capable of applying heatand pressure between the crests of the flutes of ply A and ply B so asto bond the contacting surfaces of ply A and ply B in bondina zones toform a laminate product; characterised in that the division between thecrests of the laminating roller is no more than 3 mm.

The apparatus can be adapted either to make the flutes generallyperpendicular to the machine direction as in conventional manufacture ofcorrugated laminates, or generally parallel to the machine direction.This will be specified below.

Normally the bonding is established through a lamination layer (producedby co-extrusion or by an extrusion lamination technique) in order toavoid weakening, and normally the steps of the process are adaptedeither to avoid any significant attenuation of the zones in A, oralternatively a stretching in solid state between a set of groovedrollers is adapted to produce the above-mentioned “first attenuatedzones”, whereby the grooved roller for lamination is coordinated withthe set of grooved rollers for stretching in such a way that each zoneof bonding mainly becomes located within a first attenuated zone.

The “second attenuated zones”, which have been described above in thedescription of the product, can be formed by stretching between afurther set of grooved rollers suitably coordinated with the groovedrollers which produce the first attenuated zones.

The advantages of the first and second attenuated zones in terms ofproduct properties have already been explained. For the carrying out ofthe method, the first attenuated lines allow increases of velocity andtherefore improved economy, since the zones in ply A which are going tobe bonded, have been made thinner and therefore require less heatingtime during the application of heat prior to the bonding. Furthermorethe first attenuated zones and in particular the combination of firstand second attenuated zones can be of great help for the process byacting as “hinges” in ply A. In the type of apparatus in which thegrooved roller for lamination has grooves which are generally parallelwith its axis, these “hinges” make it possible to direct even relativelyheavy A-ply into fine grooves. In the type of apparatus in which thegrooves are circular or helical, but in any case approximatelyperpendicular to the roller axis, the “hinges” help to keep ply A “intrack” during its passage from grooved roller to grooved roller, inother works the “hinges” help to coordinate the action of the groovedlamination roller with the action of the preceding set or sets ofgrooved rollers which form the flute under a simultaneous transversestretching.

While it is essential for normal uses of the invention for applicationsas a flexible film that the division on the grooved roller whichproduces the lamination on the crests is no more than 3 mm, it isgenerally recommendable to make it no more than 2.5 mm, preferably nomore than 2.0 mm and still more preferably no more than 1.5 mm.

The film or films used for ply A is preferably, prior to forming of thewaved configuration and prior to making of the first and secondattenuated zones (if such zones are made), supplied with orientation inone or both directions, the resultant main direction of orientationbeing in the direction which is selected to become the direction offluting. This can be by means of a strong melt orientation, orpreferably, alternatively or additionally by known stretching procedurescarried out in the solid state. If the process is adapted to make theflutes generally parallel with the machine direction, this will be agenerally longitudinal orientation process, which is simple, and if theprocess is adapted to make the flutes generally perpendicular to themachine direction, it will be a generally transverse orientation processwhich is much more complicated to establish and usually requiresexpensive machinery. It is noted that neither of the two closestreferences, i.e. U.S. Pat. No. 4,132,581 and Japanese patent applicationHei 02-052732 have disclosures which indicate that ply A could beoriented in a direction generally parallel with the flutes. In these twopublications the flutes are formed in the transverse direction, and hadthere been thought of using transversely oriented film it would havebeen natural to mention this, since without special steps the film isnot formed so in the extrusion or casting process.

As it already has been described in connection with the product, afurther non-waved monofilm formed or multifilm formed ply (C) ofthermoplastic polymer material can simultaneously with or subsequent tothe bonding of B to A be adhesively bonded to the crests of A on thesecond side of A. Another useful possibility is that, in a mannersimilar to the forming and application of A, there is produced a secondmonofilm formed or multifilm formed ply (D) having waved fluteconfiguration with a wavelength of preferably no more than 3 mm, and thecrests on one side of D are laminated to the second side of Bsimultaneously with or following the lamination of B with A.

In most applications of the invention the mono- or multifilm formedplies should mainly consist of polyolefin, and should be produced by aprocess involving extrusion. Furthermore the films constituting theplies should normally be made by co-extrusion in which there isco-extruded surface layers to enable the lamination without any meltingof the main body of the films.

As it also appears from the description of the product, some of theflutes at least can be flattened after the lamination. This is done atintervals, preferably under heat and pressure sufficient to bond allfilms in the laminate to each other so that the flutes with adjacentfilm material form fine elongated pockets closed at each end. Theflattening can be carried out with bars or cogs which have theirlongitudinal direction arranged transversely to the flute directionand-which each covers a number of flutes, optionally the entire width ofthe laminate.

A suitably distinct formation of the first attenuated zones can beestablished at least in part by giving the crests on the groovedstretching roller intended to produce the stripes a temperature which ishigher than the temperature of the crests on the other groovedstretching roller and/or by giving the crests on the grooved stretchingroller intended to produce the stripes a radius of curvature which issmaller than the radius of curvature of the crests on the matchinggrooved stretching roller. A significant orientation mainly in thedirection nearly parallel with the fluting, and/or a high co-efficientof elasticity (B) of ply A are also efficient means to give the firstattenuated zones suitably distinct borders.

A good way to make the fluting finer than this can be done by purelymechanical means is by use of shrinkage. Prior to the lamination ply Bis supplied with orientation generally perpendicular to the directionwhich becomes direction of fluting, and after the lamination B issubjected to shrinkage in a direction generally perpendicular to thedirection of fluting.

As it already has been stated the waved flute structure can be formed indifferent directions. Thus it can be established mainly in A'slongitudinal direction under a generally transverse orientation processby taking A through a set of driven mutually intermeshing groovedrollers, the grooves of the rollers being circular or being helical andforming an angle of at least 60° with the roller axis. It is mostpractical to make this angle about 90° or at least very close to this.This can be arranged so that A moves directly from its exit from one ofthe grooved stretching rollers which form the waving on A to the groovedlamination roller, whereby these two grooved rollers are in closeproximity to each other and have the same pitch, and are mutuallyadjusted in the axial direction. The pitch, in this aspect should bemeasured at the operational temperature of the respective roller.

Alternatively A can move from this exit from one of the groovedstretching rollers which form the waving on A to the grooved laminationroller over one or a series of heated, grooved transfer rollers. Thegrooved rollers in this row start with the grooved stretching rollersand end with the grooved lamination roller and each is in closeproximity to its neighbour or neighbours. Each of the grooved rollers inthe row-has the same pitch (measured at the operational temperature ofthe respective roller) and their axial positions are adjustable to eachother (see FIGS. 7 and 8 and the example).

When the fluting is produced in the longitudinal direction by means ofrollers with circular grooves, ply A's width measured as the direct,linear distance will remain constant from its inlet to the process ofthe lamination, apart from deviations in very narrow edge regions, whichshould be trimmed off. Therefore, the ratio between ply A's real width,measured along its curved extension, and A's linear width, which is thesame as B's width, equals the transverse stretch ratio and is related tothe thickness reductions in the attenuated zones.

However, as it already has been mentioned, the flutes can also beproduced in a distinctly transverse direction. In this embodiment, anangle of about 30° between the grooves and the roller axis is probablyabout the maximum which is practically possible, but it is simplest towork with grooves which are parallel with the roller axis.

The embodiment with grooves parallel to the roller axis is furtherdefined in method further characterized in that each grooved roller usedto form the flutes in A and A to B, and each grooved roller used to formthe first attenuated zones as described herein if such zones areproduced, and each grooved roller used to form the second attenuatedzones as described herein if such zones are formed, is a grooved rollerin which the grooves are essentially parallel with the roller axis, andmeans are provided to hold the flutes of A in the grooves in the rolleron which these flutes are formed and bonded during the passage from theposition where the flutes are formed to the position where A is bondedto B, said holding means adapted to avoid a frictional rubbing on Aduring said passage. The method can be further characterized in that theflutes in A are formed by use of an air jet or a transverse row ofairjets which directs A into the grooves on the forming roller. Themethod can be further characterized in that if first attenuated zonesare formed as described herein by grooved rollers acting in coordinationwith the grooved roller used for lamination, said coordination consistsin an automatic fine regulation of the relative velocities between therollers. The method can be further characterized in that when secondattenuated zones are formed as described herein by grooved rollersacting in coordination with the grooved rollers used to produce thefirst attenuated zones, said coordination consists in an automatic fineregulation of the relative velocities between the rollers.

The means to hold A in fluted form in the grooves from flute formationto bonding, and adapted to avoid a frictional rubbing on A, can bedevices for suction through channels from the inside of grooved roller—amethod which as already mentioned is known from making corrugatedpaperboard—or it can be use of tracks or shields which are adapted fromthe construction used in manufacture of corrugated paperboard by beingair-lubricated. This means that the tracks or shields are supplied withfine channels, or preferably a part of each track or shield is made fromporous, sintered metal, and pressurized air is blown through thechannels or pores to form an air-film on which the fluted ply can flow.

The means for fine regulation comprise a method characterized in that iffirst attenuated zones are formed as described herein by grooved rollersacting in coordination with the grooved roller used for lamination, saidcoordination consists in an automatic fine regulation of the relativevelocities between the rollers and a method characterized in that whensecond attenuated zones are formed as described herein by groovedrollers acting in coordination with the grooved rollers used to producethe first attenuated zones, said coordination consists in an automaticfine regulation of the relative velocities between the rollers, whichare similar to registration means in multicolour printing technology.

The following sections will describe different selections of theorientation and/or elasticity in the different plies, specialutilization of the channels or pockets formed by the flutes, andparticular end uses of the product of the invention.

It has already been mentioned that, in an important embodiment of theproduct according to the invention, ply A within each non-bonded zoneand outside the first attenuated zone if such zone is present, ismolecularly oriented mainly in a direction parallel to the direction ofthe flutes or a direction close to the latter.

With ply A so oriented, there are different preferable options for plyB, depending on the uses of the laminate. One very important option isthat B also is molecularly oriented and B's orientation within eachnon-bonded zone in a direction perpendicular to the direction of theflutes is higher than A's average orientation in the same directionwithin the non-bonded zone. The said two components of orientation arealso in this case, indicated by shrinkage tests.

This does not necessarily mean that ply B must have its strongestcomponent of orientation in the transverse direction, in other words thelaminate need not necessarily be a cross-laminate. Thus, ply B maysimply be highly blown film, which by means of a high blow ratio hasobtained a relatively high transverse melt orientation. The embodimentis further characterized is that the yield tension in A in a directionperpendicular to the flutes, both referring to the cross-section of therespective ply and determined in the non-bonded zones on narrow stripsat an extension velocity of 500% min⁻¹, is no less than 30 Nmm⁻² andstill more preferably no less than 75 Nmm⁻².

As mentioned there are cases, e.g., in bag construction, in which thereis a need for a high yield tension in one direction only, but combinedwith high puncture resistance. The laminate characterized in that B hasa lower coefficient of elasticity than A, both as measured in thedirection perpendicular to the flute direction or the laminatecharacterized in that the choice of B and of depth of fluting is so thatby stretching of the laminate perpendicular to the direction of thefluting up to the point where the waving has disappeared, B still hasnot undergone any significant plastic deformation, preferably B isselected as a thermoplastic elastomer are designed for this.

As it appears from the foregoing the present invention is very useful inconnection with cross-laminate, i.e. the laminate which comprises atleast two films each of which has a main direction of orientation andwhich are laminated so that the said two directions cross each other.Different ways of carrying out this aspect of the inventions are asdescribed below, from which also the method of making becomes clear: (1)a laminate characterized in that A and B each has a main direction oforientation, either by being uniaxially oriented or unbalanced biaxiallyoriented, or by in itself being a cross-laminate of uniaxially orientedor unbalanced biaxially oriented films, such cross-laminate exhibiting aresultant main direction of orientation, whereby the resultant maindirection of orientation in A is generally parallel with thelongitudinal direction of the flutes, while the resultant main directionof orientation in B forms an angle to the said direction in A; (2) alaminate characterized in that B and C each has a main direction oforientation, either by being uniaxially oriented or unbalanced biaxiallyoriented, or each in itself being a cross-laminate of uniaxially orunbalanced biaxially oriented films, said cross-laminate exhibiting aresultant main direction of orientation whereby the main direction oforientation in B crisscrosses the main direction of orientation in C;(3) a laminate characterized in that A in a non-oriented state exhibitsa co-efficient of elasticity E which is lower than E of both B and C innon-oriented state, preferably by a factor of at least 1.5 and morepreferably at least 2; and (4) a laminate characterised in that theflutes are flattened at intervals and bonded across each ones entirewidth to make the flute form a row of narrow closed pockets.

Suitable methods and apparatus for cross-lamination may be achieved bycombining the information in the above mentioned EP-A-0624126, mainly inits introduction, with the formation in the inventor's olderGB-A-1526722. Thus, with reference to FIG. 4 of the present drawings, Band C may each be films, including laminates, which exhibit a maindirection of orientation whereby B's main direction of orientationcriss-crosses with C's main direction of orientation. One of thesedirections may be parallel with the machine direction, the otherperpendicular thereto, or both may from an angle higher than 0° andlower than 90°, preferably between 20° and 70° and more preferably inthe range 25 °–65° with the machine direction. In this arrangement thewaved A supplies to the laminate stiffness against bending, but at thesame time, since it establishes a “dislocated” bonding between B and C,it also has importance for the tear propagation resistance. It is knowne.g. from the above-mentioned GB-A-1526722, that the superior tearpropagation resistance which can be obtained by cross-lamination,depends on having bonding strength which is not too high, since the tearmust be allowed to develop along different directions in the differentplies of the cross-laminate. Since on the other hand the cross-laminateshould not be prone to accidental delamination during use, as forinstance described in the said patent, there can be used a combinationof strong bonding in spots or lines and a weak bonding over the rest.However, the “dislocated” bonding of cross-laminated B and C through thewaved A can provide a better combination of high tear propagationresistance and adequate bonding strength, especially when thecoefficient of elasticity E of film A is lower than the coefficient Efor both B and C, preferably by a factor of at least 1.5 and morepreferably at least 2. Furthermore the flutes may be flattened atintervals and bonded across each ones entire width to make the flutefrom a row of narrow, closed pockets. The purposes of such flatteninghave been mentioned above.

In the above description there is mentioned the “main direction oforientation” in the films B and C. If plies B and C each are mono-films,normally with coextruded surface layers, this may be a monoaxial orunbalanced biaxial orientation. However, each of the films B and C mayalso in themselves be cross-laminates, normally 2-ply cross-laminates.

To clarify this, B may e.g. consist of two plies of equal composition,equal thickness and equal degree of orientation, but one oriented at+30° and the other at −30° to the machine direction. This will result ina main direction of orientation following the machine direction.Similarly C may consist of two equal plies, one oriented at +60° and theother at −60°. The resultant direction of orientation then isperpendicular to the machine direction.

Uniaxial or unbalanced orientation in a film can be obtained under useof spiral cutting of a tubular film with mainly longitudinal directionas disclosed in EP-A-0624126 and GB-A-1526722, both mentioned above, anddisclosed in more detail in EP-A-0426702. The latter also discloses amethod of obtaining a uniaxial or strongly unbalanced melt-orientationwhich is perpendicular to the machine direction, namely by twisting of atubular film coming out of the extrusion die followed by helical cuttingunder the calculated angle. Another embodiment of the cross-laminationaspect off the present invention is a laminate characterized in that Aand B each has a main direction of orientation, either by beinguniaxially oriented or unbalanced biaxially oriented, or by in itselfbeing a cross-laminate of uniaxially oriented or unbalanced biaxiallyoriented films, such cross-laminate exhibiting a resultant maindirection of orientation, whereby the resultant main direction oforientation in A is generally parallel with the longitudinal directionof the flutes, while the resultant main direction of orientation in Bforms an angle to the said direction in A. The expression resultant maindirection of orientation has the same meaning as explained above.

If this laminate is to be used in the construction of bags withheat-seals generally perpendicular to the direction of the flutes, andif such heat-seals may be subjected to high shock-peel forces then thelaminate should preferably be constructed as a laminate characterized inthat there is only the two mono -or multilayered films A and B and A isunoriented states exhibits a co-efficient of elasticity E which is lowerthan the E exhibited by B in unoriented state, preferably by a factor ofat least 1.5 and more preferably by a factor of at least 2. The flutedsofter A-film can then form the inner side for heat-sealing, and thestiffer, smooth B-film can form the outer side of the bag.

Another aspect of the invention (“the encapsulation/canalizationaspect”) comprises a number of embodiments which for different practicalpurposes utilize the interior cavities in the laminate, optionally incombination with suitable perforations, either to canalize a flow ofliquid or air, or to encapsulate filling material in particulate,fibrous, filament or liquid form. The latter may e.g. be a preservativefor goods packed in the flexible laminate. These different embodimentsare described in the following descriptions. The laminate ischaracterized in that at least some of the channels formed by the flutesand the matching non-waved film material, which channels may be closedto pockets, contain a filling material in particulate, fibrous, filamentor liqiuid form. Such laminates can also be characterized in that saidfilling material is adapted to act as a filter material by holding backsuspended particles from a liquid passing through the channels orpockets or is an absorbent or ion exchanger capable of absorbing orexchanging matter dissolved in such liquid, said filler optionally beingfibre-formed or yarn-formed, and that each filled flute and matchingnon-waved film material is supplied with a row of perforations, wherebythe perforations or groups of perforations in a flute and theperforations or groups of perforations in the matching non-waved filmmaterial are mutually displaced so as to force the liquid with thesuspended particles, while passing from one surface of the laminatetowards the other surface, to run through the filter material in adirection parallel to the longitudinal directions of the flutes.Geotextile substitute can also be constructed that are capable ofletting water through but withholding the soil and preferably comprisingoriented and crosslaminated films. Such geotextile substitutes arecharacterized in that said filling material is adapted to act as afilter material by holding back suspended particles from a liquidpassing through the channels or pockets or is an absorbent or ionexchanger capable of absorbing or exchanging matter dissolved in suchliquid, said filler optionally being fibre-formed or yarn-formed, andthat each filled flute and matching non-waved film material is suppliedwith a row of perforations, whereby the perforations or groups ofperforations in a flute and the perforations or groups of perforationsin the matching non-waved film material are mutually displaced so as toforce the liquid with the suspended particles, while Passing from onesurface of the laminate towards the other surface, to run through thefilter material in a direction parallel to the longitudinal directionsof the flutes. Geotextile substitute are further characterized in thatthe filler is sand. The method of making these products are described inthe following descriptions. The method is characterized in thatparticulate, liquid or thread/yarn formed material is filled into someat least of those flutes in A which, by the lamination to B, are closedto form channels, this filling taking place before, prior to or duringsaid lamination. The method can also be characterized in that afterfilling the filled channels are closed at intervals by pressure and heatto form filled pockets. The method can also be characterized in thatprior to, simultaneously with or following the filling step perforationsare made in the laminate at least on one side to help the fillingmaterial or part thereof dissipate into the surroundings or to allow airor liquid to pass through the pack of filling material. The method canalso be characterized in that there is made a row of micro perforationson each side of each filled channel, said rows being mutually displacedto force air or liquid which passes through the laminate to run adistance along a channel or pocket, and apparatus suitable for carryingout the method is is described in the following description. Theapparatus comprising a filler station between the fluting roller (s) andthe laminating roller for introducing filling material into the flutesbetween ply A and ply B. The filling station can also operate in whichthe filler material is in particulate, fibrous or yarn form.

The embodiment of the present invention in which the fine canals or“pockets” are used to “bury” preservatives, have obvious advantages overthe usual method of blending such agents with the polymers to beextruded into film form. One advantage is that the concentration of thepreservative can be much higher, another that the preservative needs notbe able to withstand the temperature of extrusion. The preservative mayreach the object to be preserved by migration alone, or if the agent issolid it may gradually evaporate and diffuse through sufficiently fineperforations or pores.

It is also customary to contain preservative agents in small bags whichare placed inside a package. Compared to this method of protection, thepresent invention has the advantage that the preservative agent can bedistributed almost homogeneously over the full area of the packingmaterial.

The filter material stated in claim 30 30. Laminate according to claim27, characterised in that said filling material is adapted to act as afilter material by holding back suspended particles from a liquidpassing through the channels or rockets or is an absorbent or ionexchanger capable of absorbing or exchanging matter dissolved in suchliquid, said filler optionally being fibre-formed or yarn-formed, andthat each filled flute and matching non-waved film material is suppliedwith a row of perforations, whereby the perforations or groups ofperforations in a flute and the perforations or groups of perforationsin the matching non-waved film material are mutually displaced so as toforce the liquid with the suspended particles, while passing from onesurface of the laminate towards the other surface, to run through thefilter material in a direction parallel to the longitudinal directionsof the flutes has many potential uses, e. g. as a geotextile geotextilesubstitute capable of letting water through but withholding the soil,constructed according and preferably comprising oriented andcrosslaminated films, where the filler is sand) but also for instancefor water treatment in the chemical industry and in gas face masks.

Although the claims relating to these filter materials, including theweather-protective laminate is made to be weather (rain and wind)resistant and air-permeable, characterised in that at least some of thechannels formed either by waved ply A and non-waved ply B and/or Cand/or waved ply D are connected to the environment on both sides of thelaminate through perforations, the perforations on the two sides of achannel being mutually displaced so as to force air or water which passthrough the laminate to run a distance through a channel, it should beunderstood that similar products having wavelength somewhat higher than3 mm also have important uses and are considered inventive new products.Thus in a further aspect of the invention there is provided a laminatecomprising at least a monofilm formed or multifilm formed ply (A) andanother monofilm formed or multifilm formed ply (B) both mainlyconsisting of thermoplastic polymer material, whereby at least Aconsists of cold-orientable material in which A has a waved fluteconfiguration while B is not waved, and B on a first side is adhesivelybonded in bonding zones to the crests on a first side of A in which theadhesive bonding has been established through a lamination layer, andthat either the thickness of A is generally the same within thenon-bonded zones as it is within the bonded zones, or A exhibits firstsolid-state-attenuated zones (hereinafter the first attenuated zones)extending parallel to the flute direction, each bonding zone mainlybeing located within a first attenuated zone, the laminate beingmoisture resistant but air permeable. The laminates are useful forforming raincoats and tarpaulins. Other uses in which an additive isincorporated into the flutes are described below.

Other important uses of the invention are for bags and self-standingpouches. In this connection, reference is made to the followingproducts: (1) a bag made from the laminate of this inventioncharacterized in that the laminate comprises only the two mono -ormultifilin formed plies A and B, and in that the bottom and top of thebag are generally perpendicular to the longitudinal direction of theflutes; (2) a self-standing bag or pouch made from the laminate of thisinvention, in which the bottom of the bag or pouch is gusseted, andfront and back faces of the bag or pouch are adhesively joined at theiredges preferably by heat-sealing, characterised in that the laminatecomprises only the two mono -or multifilm formed plies A and B, and inthat the bottom and top of the bag or pouch are generally parallel withthe longitudinal direction of the flutes; and (3) a self-standing bag orpouch characterized in that the capability of the bag or pouch to standon its own is enhanced by flat-pressed lines generally perpendicular tothe longitudinal direction of the flutes.

For all uses of the present invention, a very interesting andwear-resistant print can be obtained when, prior to the lamination, Aand/or B is supplied with print on the surface to become the inside ofthe laminate, the printing process being in register with theflute-forming and lamination processes so as to limit the printgenerally to the non-bonded zones. This durable print may form a text, adecorative pattern or simply lines which accentuate the fluting or thetextile-like appearance of the laminate. Special decorative effects canbe achieved if the print provides a metallic appearance or amother-of-pearl effect.

The invention shall now be explained in further detail with referencesto the drawings.

FIGS. 1, 2, 3, 4 and 5 are cross-sections representing four differentstructures of the laminate of the invention, comprising the miniflutedply A, or plies A and D, and the straight ply B or plies B and C. Theflutes in each of these structures can extend longitudinally ortransversely, seen in relation to the machine direction of theflute-forming and laminating machinery.

FIG. 6 is an enlarged detail of FIG. 1 to illustrate how these pliesthemselves can be laminates of films, and how these films can bemultilayered as made by co-extrusion, this being done to facilitatebonding and lamination.

FIG. 7 is a principal sketch representing the steps from formation ofthe miniflutes in A to lamination of A with B in the manufacture of theproduct shown in FIG. 2, the different steps being represented by thecross-sections of the films A and B and by the cross-sections throughthe axis of the rollers of the surfaces of the rollers.

FIG. 8 is a sketch of the machine line corresponding to FIG. 7 withaddition of the means to laminate straight film C to A opposite to B.

FIGS. 9 a, 9 b and 9 c are sketches illustrating the cross-laminatecharacterized in that A and B each has a main direction of orientation,either by being uniaxially oriented or unbalanced biaxially oriented, orby in itself being a cross-laminate of uniaxially oriented or unbalancedbiaxially oriented films, such cross-laminate exhibiting a resultantmain direction of orientation, whereby the resultant main direction oforientation in A is generally parallel with the longitudinal directionof the flutes, while the resultant main direction of orientation in Bforms an angle to the said direction in A.

FIGS. 10 a, b and c represent sections parallel to the flutes andthrough the middle of a non-bonded zone, showing applications of theinvention in which the channels or pockets formed between ply A and plyB are used as mini-containers or to canalize a flow of air or water,namely in FIG. 10 a as mini-containers for a protective agent, in FIG.10 b for filtration and in FIG. 10 c for weather protection.

FIG. 11 shows a modification of the lamination station of FIG. 8 inwhich there are added filling devices to fill particulate material intothe flutes before the lamination, and added sealing equipment to formtransverse seals after the lamination, thereby making closed pocketswhich serve as “mini-containers” for the particulate material.

FIG. 12 is a flow-sheet showing a process for producing the laminatewith transverse fluting and with “first” and “second” attenuated zones(as these expressions have been defined).

FIG. 13 shows a detail of a grooved lamination roller for formation oftransverse fluting, air jets being used to direct the ply into thegrooves and vacuum being used to retain it there.

With references to FIGS. 1 to 5 it should be mentioned for the sake ofclarity, that the wavelength referred to in the foregoing and in theclaims, is the straight linear distance from x to z. This distance ispreferably 3 mm or lower, and as it appears from the example, theinventor has been able to make it as small as 0.8 mm, which howeverneeds not be the ultimate lower limit obtainable and useful. It is notedthat U.S. Pat. No. 5,441,691 (Dobrin et al.) makes embossed film (notheat-bonded laminates) having a generally circular shape of the bosses,with a spacing from centre to centre which can be still finer than these0.8 mm, however the bosses of this patent are drawn much thinner thanthe main body of the film.

In FIG. 1 the thickness of ply A is generally the same across the ply.In case of transverse fluting this can be achieved by the process shownin FIG. 12 (without preceding formation of attenuated zones) howeverthere is a limit, which is of practical importance, of how fine thewavelength can be, seen in relation to the thickness of ply A.

In case the flutes are made parallel with the machine direction, forformation of the flutes and the lamination is preferably carried outgenerally as shown in FIG. 8. This means there will always be atransverse stretching between intermeshing grooved rollers, and thedegree of fluting will correspond to the degree of stretching. When filmis stretched between very fine grooved rollers, there will be a strongtendency to localize the stretching entirely or predominately on andnear to the tips of the grooves. This can be avoided, but withdifficulty, by using film which in a preceding process has beentransversely stretched, and feeding the film unto the roller at atemperature which is higher than the temperature of the roller.

However, in the laminate structures shown in FIGS. 2 to 5 thedifferences of thickness resulting from grooved roller stretching hasbeen utilized in a way which generally is an advantage for theproperties of the product. By the exact registration between the groovedrollers for stretching, the grooved roller for lamination and a groovedtransfer roller therebetween, it is arranged that each bonding zonemainly falls within an attenuated zone. As it appears from FIG. 3 therecan be two sets of attenuated zones for each zone of bonding, namely aseries (6) of wider ones (“the first attenuated zones”) within which thebonding zones fall, and a set of shorter ones (101), the latter referredto as the “second attenuated zones”.

By attenuating ply A at the basis where it is bonded to ply B, thethickness of A is minimized at the location where its contribution tostiffness in the stiff direction in any case is insignificant. Byintroducing the narrow “second attenuated zones” which act as “hinges”,the cross-section becomes almost triangular as shown in FIG. 3. Thismeans that the stiffness is further improved. These attenuated zonesalso introduce a tendency in the material to stretch rather than ruptureunder impact actions.

To clarify the concepts, each first attenuated zone (6) is perdefinition delimited by the locations (102) where the thickness of ply A(or ply D) as indicated by arrows is the average between the smallestthickness in this zone and the highest thickness in the adjacentnon-bonded zone.

Structures with “first attenuated zones” as shown in FIGS. 2 to 5 andstructures with both “first and second attenuated zones”, as shown inFIGS. 3 can also be produced with machinery which make transversefluting. This shall be described later.

In FIG. 6 both plies A and B are in themselves laminates, for instancecross-laminates characterized in that A and B each has a main directionof orientation, either by being uniaxially oriented or unbalancedbiaxially oriented, or by in itself being a cross-laminate of uniaxiallyoriented or unbalanced biaxially oriented films, such cross-laminateexhibiting a resultant main direction of orientation, whereby theresultant main direction of orientation in A is generally parallel withthe longitudinal direction of the flutes, while the resultant maindirection of orientation in B forms an angle to the said direction in A,and each film from which the plies are produced is co-extruded.Therefore A and B are each formed by a lamination process(the“pre-lamination”) prior to the lamination of A to B. Layer (1) is themain layer in each of the two coex films which make A, and layer (2) isthe main layer in the two coex films which make B. Layers (1) and (2)can e. g. consist of high density polyethylene (preferably HMWHDPE) oriso-or syndio-tactic polypropylene (PP) of blends of one of thesepolymers with a more flexible polymer, for instance, for HMWHDPE, LLDPE.If stiffness is the most preferred property of the minifluted laminate,plain HMWHDPE or plain PP may be chosen, but if tear and punctureproperties play a more important role and/or superior heatsealproperties are essential, the mentioned blends may be more suited.

Layers (3) are coextruded surface layers with the function to improvethe heat-seal properties of the finished, minifluted laminate and/ormodify its frictional properties. Layers (4) are co-extruded surfacelayers (“lamination layers”) with the two functions: a) to facilitatethe pre-lamination and b) to control the bonding strong, otherwise thetear propagation strength suffers).

Similarly, layers (5) are co-extruded surface layers to facilitate thelamination of the entire A to the entire B and control the strength ofthe bonding between A and B.

With reference to FIG. 7 and FIG. 8 the structure shown in FIG. 2 can beformed by passing film (A) first over the grooved pre-heating roller (6a) which heats it only along the lines which shall become attenuated,then over the grooved stretching rollers (7) and (8), further overgrooved transfer and flute-stabilizing roller (9), and finally overgrooved lamination roller (10) and its rubber-coated counter-rollers(11), while film (B) is passed over the smooth rollers (12) and (11).The grooves of all of the rollers are circular so that the flutes areformed in the machine direction. If B is transversely oriented andtherefore has a tendency to transverse shrinkage, rollers (12) and (11)are preferably supplied with devices, e.g. belts, to hold the edges (notshown). All of these rollers are temperature controlled rollers, rollers(9), (10), (11) and (12) being controlled at the lamination temperature,rollers (6 a) and (8) at a somewhat lower temperature and roller (7) ata temperature about 20 or 30° C. (There can be further rollers forpreheating of B). By choice of suitable, coextruded surface layers—see(5) in FIG. 6—the lamination temperature is kept far below the meltingrange of the main layers in (A) and (B). The temperature of the zones(6) in (A) during the transverse stretching between rollers (7) and (8)is preferably still lower, e.g. in the range of about 50–70° C. and therest of (A) much lower, e.g. around room temperature, as it also appearsfrom the mentioned roller temperatures. If the main layers in (A) and(B) consist of plain HDPE or blend of HDPE and LLDPE, the laminationtemperature is preferably chosen between about 80 and about 110° C., andthe coextruded lamination layers, which can consist of a suitable plainor blended copolymer of ethylene, are chosen to produce lamination atthis temperature.

The crests on roller (8) has very small radius of curvature, e.g. about0.05 mm or an extremely narrow “land”. The crests on roller 6 a whichhave the function to preheat, may, depending on the film, be similar orsomewhat rounder or with a slightly wider land. The crests on rollers(7) and (9) have a higher radius of curvature or a wider land, to avoidtransverse stretching on these crests. Suitable values for the sizes ofthe grooves are mentioned below in the example.

The different temperatures on the different grooved rollers causedifferent thermal expansions, compared to a state where all have roomtemperature, and this must be taken into consideration when the groovedrollers are constructed, since they must fit exactly to each otherduring operation. (10° C. heating of a 10 cm long steel roller segmentcauses about 0.011 mm expansion of this segment). Reference is againmade to values in the example.

Rollers (7), (8) and (10) are driven, while rollers (6 a), (9), (11) and(12) may be idling.

As it will be understood, the attenuation of A in the zones (6) takesplace almost entirely by the transverse orientation at a temperatureessentially below the melting range of the main body of A. Thisattenuation therefore does not cause any significant weakening of A'stransverse strength, contrarily it will normally cause an increase ofthis strength. After the transverse stretching on the crests of roller(8) the width of the “first attenuated zones” (6) should preferably notexceed (as a rule of the thumb) half the wavelength, but the degree ofstretching should normally be as high as practically obtainable, whilethe degree of transverse stretching between the “first attenuated zones”normally should be as low as practically obtainable, with the intendedresult that ply A in the unbonded zones becomes as thick as the chosensquare metre weight of A allows and the flutes become as high aspossible.

A practical way of achieving that the first attenuated zones and thezones of bonding match with almost equal width is the following: therelatively flat crests on the laminating roller (10) are made slightlywider than the chosen width of the first attenuated zones, and thetemperature and velocities are adjusted to each other in such a way thatthe first attenuated zones (6) become heated to a temperature at whichthe material will laminate with B, while the thicker A-ply between zones(6) does not reach a temperature at which lamination can take place.

The use of longitudinally oriented A-ply as in claim 6 will impart atendency in A to “neck down” and form thin longitudinal lines when A isstretched transversely. Therefore, longitudinally oriented A-ply willenhance the possibilities of getting a sharp distinction betweenstrongly attenuated zones (6) and non-attenuated ply A between thesezones.

Theoretically there will always occur some attenuation also of the B-plyin the zones of bonding, since the bonding is established underpressure, but this attenuation has no positive effect and shouldpreferably not exceed 20%. Due to the presence of lamination layers (see(5) in FIG. 6) such attenuation of the B-ply can be made negligible.

In FIG. 8 the minifluted laminate leaving lamination rollers 10 and 11is marked (B/A), In this figure it proceeds for lamination inconventional manner with the non-waved, mono-/or multilayered film Ccoming from the smooth steel roller (13). The lamination takes placebetween the smooth steel rollers (14) and (15) of which at least roller(14) is heated to a convenient lamination temperature and is driven. Thewaved film A is heated to lamination temperature, at least on its freecrests, by means of hot air from the blower (16). Rollers (14) and (15)are kept at a distance from each other which is small enough to effectthe lamination but big enough to avoid excessive flattening, e.g.between 0.2 and 0.6 mm. When A, B and C are very thin films, e.g. eachin the range of 0.03–0.10 mm thick (for A this refers to the non-wavedform) such conventional lamination would have been very difficult due tothe floppiness of waved A, but since the flutes now have beenconsolidated by the bonding to B, the lamination of A to C presents noparticular difficulty.

The laminate leaving the lamination rollers (14) and (15) is markedB/A/C. It is cooled, e.g. by air (not shown) and may normally be reeledup or flip-flopped, since it normally is sufficiently flexible materialalthough fluted, or it may directly be cut into lengths.

To make the laminate shown in FIG. 5, one option is to make the A/Blaminate shown in FIG. 2, and laminate this over the rollers (11) and(10) with the fluted ply D leaving roller (9). This requires exactregistration between the rollers which make the A/B laminate and roller(1)). Alternatively B can consist of e.g. two films B1 and B2. Then intwo mutually independent processes there are made an A/B1 laminate and aD/B2 laminate, and the two are bonded together with B1 against B2 in anextrusion lamination process.

With certain modification the line shown in FIGS. 7 and 8 can also beused to make the laminate of FIG. 3, which has “second attenuatedzones”. For this purpose roller (6 a) should have the same surfaceprofile and the same low temperature as roller (7), and it should bepreceded by and in slight engagement with a roller with the same surfaceprofile as roller (8), which roller should have the same highertemperature as roller (8).

In the minifluted “multi-crosslaminate” shown in FIGS. 9 a, 9 b and 9 c,the two coextruded films (1 a) and (1 b) from which A is made by“pre-lamination”, are oriented in criss-crossing directions, which forman angle lower than 45° with the longitudinal direction (the flutedirection) as symbolized by the arrows (1 aa) and (1 bb). This gives aresultant main orientation direction for A parallel with the flutedirection, symbolized by the arrow marked A′. Similarly the twocoextruded films (2 a) and (2 b) from which B is made by“pre-lamination”, are oriented in criss-crossing directions, which forman angle higher than 45° with the flute direction, as symbolized by thearrows (2 aa) and (2 bb). This gives a resultant main orientationdirection of B perpendicular to the flute direction, symbolized by thearrow B′.

In FIG. 10 a, which as mentioned shows a longitudinal section through aflute in ply A, the latter has been flattened and sealed to ply B atintervals (103) to form pockets or “mini-containers”, and thesemini-containers have been filled with a particulate substance (104)which has a purpose for the use of the laminate, e.g. for protection ofmaterial packed or wrapped up in the latter. As one among many optionsit may be an oxygen scavenger. To enhance the action of the substancethe flutes may be supplied with fine perforations on the side towardsthe packed product. The substance may also e.g. be a fire retardantmaterial such as CaCl₂ with crystal water, or just fine sand to increasethe bulk density of the laminate.

FIG. 11 which shall be described below, shows how the particulatesubstance can be fed into the flutes of ply A prior to its laminationwith ply B, and how the flutes can be closed to pockets by transversesealing after the lamination, without any essential contamination ofthese transverse seals.

A laminate between a fluted thermoplastic film and a non-flutedthermoplastic film with a filling material between is known fromJapanese Patent publication No. 07-276547 (Hino Masahito). However, inthis case the filling material is a continuous porous sheet (forabsorption) which extends from flute to flute without interruptions, sothat there is no direct bonding between the flute and the non-flutedfilms. One of the thermoplastic films is first directly extruded untothis porous (e.g. fiberformed) sheet, then the two together are given afluted shape between gear rollers while the thermoplastic film still ismolten, and finally a second thermoplastic film is extruded directlyunto this fluted assembly to join with the porous sheet. Hereby thebonding necessarily must be very weak, and the mechanicalcharacteristics must be completely different from those of the presentproduct. The wavelength of the fluting is not indicated.

In the technical filter material for liquid or gas flows shown in FIG.10 b there is inserted a strand or yarn into each flute—in connectionwith the description of FIG. 11 it shall be explained how that can bedone—and both sides of each channel formed by fluted ply A andnon-fluted ply B is supplied with a row of perforations, (106) in ply Aand (107) in ply B. These rows are mutually displaced as shown so thatthe liquid or gas passing from one surface of the laminate to the other,is forced to follow a channel over a distance corresponding to thedisplacement. The fitting between the yarn and the channel may beimproved by shrinkage of A and/or B after the lamination process.

The pocket structure shown in FIG. 10 a can also be used for filtrationpurposes if ply A and ply B are supplied with mutually displaced holes.Then the particulate substance (104) can e.g. consist of activecharcoal, or an ion-exchange resin, or for simple filtration purposesfine sand. Also in this case a tightening of the passage by means ofshrinkage can be advantageous or may even be essential.

Practical examples of the use of such filter materials are for airfiltration systems including absorption of poisonous substances, andion-exchange processes. In both cases the laminate can have the form ofa long web which is slowly advanced transversely to the flow whichpasses through it.

Another practical use is as a substitute of geotextiles e.g. for roadconstructions. Such textiles must allow water to penetrate but hold backeven fine particles. The present laminate, e.g. filled with fine sand inthe pockets, is suitable for this use.

For such filtration purposes, high puncture strength will often beneeded, and the laminate then preferably comprises oriented,cross-laminated films.

For the filtration purposes the condition that the wavelength should notexceed 3 mm, is often less important since appearance and handle may notbe a primary concern as it is in the case of laminates for ordinarytarpaulin uses.

The weather protective laminate shown in FIG. 10 c, e.g. for raincoats,also has a pocket structure, whereby ply A is heat-sealed to ply B bytransverse seals at locations (103), but there is no particulatesubstance in the pockets. Like the laminate for filtration, each line ofpockets is supplied with perforations in a displaced system, here shownas groups of perforations (109) in A and similar groups (110) in B, andthese groups are mutually displaced. In this sketch it is consideredthat ply A is on the side where it rains, and a person, animal or item,which the laminate shall protect, is on the ply B side. (It could be theother way round). It is also considered that the direction shown byarrow (108) is upward. Since the perforations (109) are at the bottom ofthe pockets, and because of the gravity force, only the bottom of thepockets may be filled with rainwater, while in principle no water willreach the perforations (110). On the other hand there is free passage ofair and transpiration between the hole groups (109) and (110). Also inthis product the wavelength may to some extent exceed 3 mm.

The modification of the FIG. 8 machine-line, which is shown in FIG. 11,is adapted to fill a particulate substance (104) into the channelsformed between A and B. The filling is here shown very schematically.The powder (104) is taken from a hopper (111) and is administered bymeans of an adjustable vibrator (not shown). It falls into the flutedply A at the upper side of the grooved lamination roller (10). Atregular time intervals hopper (111) is filled up with the powder (104).The means for this are not shown. Other conventional systems foradministering the powder (104) onto ply A on roller (10) may of coursebe chosen.

Roller (10) vibrates (means not shown) so that the powder is moved fromthe higher zones, i.e. those which become bonded zones when A meets B inthe nip between (10) and (11), into the lower zones, which become the“channels”.

Having left the laminating rollers (10) and (11). The A+B− laminate withpowder (104) in the channels moves towards the cog-roller (113)—itssurface is shown in a detailed part-drawing—and its rubber-coatedcounter-roller (114) which together flatten and close the channels bymaking transverse seals. Roller (113) is vibrated in order to removepowder away from the channel-parts which become flattened and sealed.

Both rollers (113) and (114) are heated to a temperature needed for thesealing, and since the laminate while entering these rollers still is atabout a temperature suitable for heat-sealing due to the previoustemperatures, this second heat-seal process needs not cause adeceleration of the entire process.

Ply A and/or ply B may be perforated by means of pin-rollers afterrollers (10)/(11) and in front or after the pair of rollers (113)/(114).In case mutually displaced rows of perforations are needed (see FIGS. 10b and c) and pin-rollers for ply A and ply B must be suitablycoordinated, and in case the perforations should have a fixed relationto the transverse seals (see FIG. 10 c, the pin-rollers must becoordinated with roller (113).

In order to make the product shown in FIG. 10 a, rollers (113) and (114)are omitted or taken out of function, and instead of administeringpowder into ply A, there is at the same place laid a yarn into eachflute. Each yarn is taken from a separate reel.

At some stage after rollers (10)/(11), ply A and/or play B may besubjected to transverse shrinkage. If this is done with ply A only, itmay be sufficient to heat the ply A-side of the laminate to an adequatetemperature by means of hot air or on one or more hot rollers. If ply Bshould be involved in the shrinkage it may be necessary to hold thelaminate at the edges while it shrinks. This may be done by means of anordinary tenterframe, but the latter should be set up to work.“inversely” so that the width gradually is reduced instead of increased.

The methods applied for making pockets from the flutes, fill powder intothese flutes, and making suitable perforations, have been explained inconnection with the longitudinally fluted laminate. Analogous methodscan be applied in connection with a transversely fluted laminate (thegeneral method of making such laminate appears from FIG. 12), and inthat case the closing of the channels to form pockets may take place byuse of a circularly or helically grooved roller. However, it is notconsidered practically possible to lay down yarn in transverse flutes atindustrially acceptable velocities.

The process for making the transversely fluted laminate, which appearsfrom the flow-sheet FIG. 12 is generally analogous to the process whichis described in connection with FIGS. 7 and 8, and the profiles of thegrooved rollers can also be generally similar, except that for theprocess of FIG. 12 the grooves extend axially, while for the process ofFIGS. 7 and 8 they are circular.

Step 1: Ply A is longitudinally stretched in very narrow zones localizedon the tips of a hot roller which has a profile similar to that ofroller (8). The grooved counter-roller, which is cold, has a profilelike that of roller (7).

Step 2: The warm, stretched “second attenuated zones” are cooled on acold grooved roller which also has a profile like that of roller (7),and then to form “first attenuated zones” between the “second”, ply A islongitudinally stretched between this cold roller and a warm groovedroller which also has a profile similar to that of roller (8). Thestretching is localized to the tips of this roller. Similar to theregistration in printing technology, step 2 is brought in registrationwith step 1 under use of a device which optically detects the stretchedzones.

Step 3: The flutes are first formed in the grooves of a hot roller witha profile similar to that of roller (10), e.g. under use of compressedair, and are held in the grooves e.g. under use of a vacuum, all asexplained in connection with FIG. 13, and ply A is then laminated withply B between the crests of this grooved roller and a rubber-coatedcounter-roller, which also is heated. Ply B has been preheated.

There can be different after treatments as explained in the foregoing.

In FIG. 13, ply A which has been supplied first with the very narrowtransverse “second attenuated zones” (101), and then with the somewhatwider, also transverse “first attenuated zones” (6), is directed intothe grooves (115) of the heated lamination roller by means of compressedair from a row of nozzles of which one (116) is shown. By use ofregistration means, working on basis of optical detection of zones (6)or (101) it is arranged that the first attenuated zones (6) will coverthe crests (118) of the grooved roller. The two sets of attenuated zonesact as hinges so that even a quite heavy ply A may be bent and form theflutes. The latter are held in shape in the grooves under use of vacuumapplied through channels (117) from the interior of the roller. Thus plyA is moved in flute shape to the nip (not shown) between the groovedroller and the rubber-coated counter-roller, where lamination takesplace. The vacuum in the grooves is adjusted so that ply A is heldfirmly when this is needed, but can be released where that is needed.There can also be a valve arrangement inside the grooved roller toeliminate the vacuum during the release.

EXAMPLE

A 2-ply laminate of fluted ply A and non-fluted ply B with Alongitudinally and B transversely oriented is manufactured on apilot-unit constructed as shown in FIGS. 7 and 8, but terminating afterthe lamination of A and B have taken place. Both plies consist of onecoextruded, cold-stretched 0.037 mm thick film consisting of HDPE with athin layer on one side, consisting of an ethylene copolymer having amelting range between 95–105° C. This is used as lamination layer in theprocess. The cold-stretching was carried out near room temperature at adraw ratio about 3:1 and was followed by heat stabilization, all byconventional means, and while the film had flat tubular form. The tubewas longitudinally cut to form ply A.

Processes for continuous manufacture of transversely oriented film arewell-known and mentioned in the foregoing, but it would have causedpractical complications for the inventor to have such film manufacturedaccording to his specifications, and therefore short lengths of the plyA-film were glued together edge to edge with a pressure-sensitiveadhesive to form a transversely oriented web.

All of the grooved rollers have the pitch 1.1000 mm at the temperatureat which they actually are used, but due to the large temperaturedifferences during the stretching/laminating process, the thermalexpansion had to be taken into consideration when these rollers weremachined at 20° C., see the table below. The biggest temperaturedifference between the rollers, as it appears from this table, is 85°,and this corresponds to an expansion of about 0.10 mm per 10 cm rollerlength, while the accumulated error in the fitting between adjacentrollers from end to-end of the rollers must be maintained lower than0.15 mm to obtain the needed registration.

The table below also indicates the radius of curvature (R) or the lengthof a “land” on the crest of each grooved roller, as seen in the axialsection in FIG. 7.

Roller No. 6a 7 8 9 10 Crest land R = 0.2 land R = 0.15 Land mm 0.4 0.150.7 Temperature 70 20 70 105 105 ° C. Pitch mm 1,0993 1,1000 1,09931,0988 1,0988

It is of course not practically possible to achieve such a high accuracyin the pitch seen individually from groove-to groove, but it isessential that errors in the pitch do not accumulate by more than 0.05mm. This is best achieved when the surface parts are made from segmentsand accumulated errors are eliminated by fine grinding of the segmentends and/or thin shims (foils) are inserted between the segments. In theactual pilot machine the length of the grooved part of each rollersurface was about 450 mm and was assembled from 3 segments. It is judgedthat in an industrial machine the rollers can be made in up to about 5 mlength, but in that case the accuracy from end to end has to be checkedwith laser measurements and adjustments made as explained.

The transverse stretching, which is the basis for the flute-formationand which forms the “first attenuated zones”—later the zones whichbecome bases, not crests of the flutes in the laminate—takes place bythe intermeshing between rollers (7) and (8) and becomes localized to azone on and nearby the crests of roller (8). This is because roller (8)is hot and has a relatively sharp crest, while roller (7) is cold andhas a much rounder crest (higher radius of curvature R). It is relevantalso in this connection that ply A is uniaxially oriented in the machinedirection and therefore has a high tendency to “neck-down” and formsharply delimited attenuated zones when it is transversely stretched.

The function of roller (6 a) is to preheat the zones which are to bestretched on the tips of roller (8). In this example the “land” on thecrests of roller (6 a) are wider than the “land” on the crests of roller(8). This has been chosen in order to counteract the very pronouncedtendency in the film to “neck-down”, in other words, to make the limitsof the “first attenuated zones” smoother. In other cases e.g. when ply Ahas a pronounced transverse orientation and therefore no tendency to“necking down” by transverse stretching, the “land” on the crests ofroller (6 a) which preheats the film, should be no wider than the “land”on the crests of roller (8).

Between rollers (6 a) and (7) there is a slight but almost zeroengagement to avoid wrinkles without stretching the films.

Having left the transverse stretching roller (8), ply A is taken over bytransfer roller (9). This is heated in order to help the shaping offlutes in the zones which have not been stretched. At this-stage the“first attenuated zones” are still deeply curved, but when (A) is takenover by the flat 0.4 mm wide crests (lands) on the grooved laminatingroller (10) the “first attenuated zones” are flattened almost over theirentire width except at their boundaries where the thickness graduallyincreases, and by means of the rubber-coated counter-roller, which onits surface has temperature 80° C., this flat portion is laminated tothe transversely oriented ply B.

Prior to the experimental run the axial position of the grooved rollersare very carefully adjusted to each other, and so is the intermeshingbetween adjacent grooved rollers. The intermeshing between rollers (7)and (8) is set to make the depth of the fluting 0.40 mm, as measured inmicroscope on a cross-section of the finished laminate.

When leaving the stretching/laminating apparatus, the miniflutedlaminted is aircooled and is reeled up on a core of diameter 250 mm. Inthe test report below this laminate is called “Sample I”.

It is noted that although the pitch of each grooved roller in the lineis 1,1000 mm referring to the temperature at-which the roller hasbeen-operated, the wavelength of the fluting in the final miniflutedlaminate, due to transverse shrinkage, is only 1.0 mm.

As a principal experiment there is out specimens of this film, 30 cmlong in the machine direction and 20 cm wide in the transversedirection, and these specimens are subjected to further transverseshrinkage by a primitive arrangement which imitates an “inverse”operation of a tenter frame. The two 30 cm long edges are fixed to twosticks, which are held by hand, and an even shrinkage is arranged bymoving the specimen over a roller surface, which is heated to 115° C.,with the B film contacting the roller. Hereby the wavelength is reducedfrom 1.0 mm to 0.8 mm.

Sample II, made for comparison: By a relatively primitive arrangementthere is made specimens of corrugated board material from the same filmas used to make “Sample I” (coextruded coldstretched HDPE-film ofthickness 0.037 mm), with all dimensions of sample A, namely as follows:

Wavelength Bonded Zones Flute-depth Sample mm mm mm I 1.0 0.4 0.4 II 5.52.2 2.2

It is noted that II's wavelength, 6.0 mm, is slightly less than theminimum mentioned in patent literature namely in U.S. Pat. No.4,132,581.

In both samples I and II, the direction of orientation in ply A isparallel with the flutes, and the direction of orientation in B isperpendicular to the flutes.

Sample B is manufactured with a small laboratory machine constructed asexplained in connection with FIG. 13, but in this case there has-nowbeen any need to make “first attenuated zones” and “second attenuatedzones”. The flutes become perpendicular to the machine direction. Likethe grooved laminating roller (10) used in the manufacture of sample I,this grooved laminating roller is heated to 105° C.

Sample III, made for comparison: The same film (coextruded orientedHDPE, 0.037 mm thick) is crosslaminated with itself without any flutingbeing made.

Comparisons Between Samples I, II and III:

Appearance and Handle:

(II) looks and feels like a board material, but is instable when bent orcompressed between the fingers.

(I) has a rather textilis look, can stand a substantial amount ofbending and compression between the fingers without changing itscharacter, and it has a feel of “bulk”.

Bending Tests:

(I) and (II) are bent over cylindrical bodies of different diameters,and it is examined how small that diameter can be before the flutesbegin to collapse in a non-elastic manner, i.e. so that there remainmarks in the flutes after the specimen has been straightened out again.

(II) can withstand bending down to a diameter of 250 mm, while (I) canwithstand bending down to a diameter of 50 mm.

Stiffness Measurements:

10 cm long specimens are cut out from samples (I), (II) and (III).

The specimens from sample (I) each comprises 20 flutes and at the edgesa bonded zone. The width of these specimens is 21 mm.

The specimens from sample (II) each comprise 4 flutes and at the edges abonded zone. The width of these specimens is 23 mm.

The width of each sample (III) specimen is 21 mm.

For controlled bending of the specimens there is made a very lightweightsupport arrangement comprising two supports with 50 mm spacing between.This support arrangement is placed on the table of a letter balance. Thebending is effected by means of a cylinder which has a diameter 50 mmand starts pressing at the middle of the supported sample. This cylinderis assembled on a stand and can be moved up and down. Correspondingvalues of the depression in mm and the resisting force in grams aremeasured and plotted. Up to a certain limit there is a lineardependence, and from the declination of the line and stiffness iscalculated as grams force per mm depression.

In order to obtain reliable reading for sample (III), 10 specimens arelaid one on top of the other. The value of stiffness is determined forthis bunch and divided by 10.

Results

Surprisingly samples (I) and (II) show the same stiffness, namely 1.6gram per mm, while sample (III) shows 0.13 gram per mm, in other wordsthe present invention has magnified the stiffness in one direction by afactor of about 12, as measured by this method.

It should have been expected that sample (III) would have shown higherstiffness than sample (I). When this is not the case, the explanationprobably is that the flutes may have been pressed relatively flat rightfrom the beginning of the depression, although in elastic manner.

In the characterisation of the product and method of the invention, ithas been emphasised that the wavelength of the fluted ply A or the pitchon the grooved laminating roller should be no more that 3 mm in order togive the corrugated laminate the character of a flexible film ratherthan a board material. However, in connection with the description ofthe filter material, in which liquid or gas passes from holes in one plyto displaced holes in the other ply, and on the way passes a filler, itwas nevertheless stated that for such purposes the wavelength may exceedthe 3 mm. Similar is true for the described weather protectivecorrugated laminate, in which there also are displaced holes, butusually no filler, and the gravity force is used to “filter” therainwater from the passing air.

Furthermore, the making of “first attenuated zones” and optionally also“second attenuated zones” has been explained as useful measures forobtaining the “miniflutes”, be it in connection with longitudinally ortransversely fluted laminates. Since these zones act as “hinges”—seee.g. FIG. 13—they enable for a given thickness of ply A a finerwavelength and/or deeper fluting then it otherwise could be achieved. Inthe foregoing there has also been stated other useful effects of the“fist attenuated zones” and the “second attenuated zones”, and it isclear that similar advantages can be achieved when the wavelength of theproduct or the pitch of the grooved lamination roller exceeds 3 mm.

Therefore the product and the making of the “first attenuated zones” andoptionally and “second attenuated zones” placed as it has been describedin the foregoing, is considered an invention independently of thewavelength.

1. A laminate comprising at least one ply A and at least one ply B eachformed of at least one monofilm or multifilm and comprising athermoplastic polymer material of which the polymer material of at leastone ply A is cold-orientable has a wavy or fluted configuration while atleast one ply B is not waved, the fluted ply A being adhesively bondedto a first side of at least one ply B in bonded zones along at leastsome of the crests of the flutes of a first side of the fluted ply A,the thickness of the fluted ply A being of a variable thicknessestablished by solid-state attenuation of the fluted ply A intransversely spaced apart elongated first attenuated zones extendingparallel to the length of the flutes, to thereby reduce the thickness ofthe fluted ply A in the first attenuated zones from that innon-attenuated zones, where each bonded zone being mainly located withina first attenuated zone.
 2. The laminate according to claim 1, whereinthe the fluted ply A exhibits within the non-bonded zones an averageyield tension parallel to the flute direction which at an extensionvelocity of 500%/min is not less than 30 Nmm².
 3. The laminate accordingto claim 1, wherein a wavelength of the flutes of the fluted ply A is nogreater than 50 times a greatest thickness of the fluted ply A within aflute.
 4. The laminate according to claim 1, wherein a dimension of thebonding zones transverse to the fluted direction is at least 15% of thewavelength of the flutes.
 5. The laminate according to claim 4, whereina transverse dimension of the non-bonded zones of the fluted ply A asmeasured along the curvature thereof between edges of two adjacentbonded zones is at least 10% greater than the linear distance betweenthe edges.
 6. The laminate according to claim 1, wherein the fluted plyA within each non-bonded zone and other than in the solid-stateattenuated zones is molecularly oriented in a direction at leastsubstantially parallel to a direction of the flutes.
 7. The laminateaccording to claim 6, wherein at least one ply B is molecularly orientedwith an orientation within each non-bonded zones perpendicular to theflute direction being greater than the average orientation of the ply Ain the same direction, the two orientations being determined byshrinkage measurements.
 8. The laminate according to claim 7, wherein ayield tension of the fluted ply A and at least one of the ply B indirections parallel to and transversely to the flute direction,respectively, are at least 30 Nmm², as determined on narrow stripswithin the non-bonded zones at an extension velocity of 500% /mm.
 9. Thelaminate according to claim 1, wherein the ply B has a lower coefficientof elasticity than the fluted ply A, both measured perpendicular to theflute direction.
 10. The laminate according to claim 7, wherein thepolymer material for the ply B and the depth of fluting in the flutedply A are so selected that when the laminate is stretched perpendicularto the flute direction sufficient to remove the fluting from the flutedply A, ply B remains free of significant plastic deformation.
 11. A thelaminate according to claim 1, wherein at least two films in the plieseach have a main direction of orientation and are arranged in thelaminate with the main directions thereof crossing one another.
 12. Thelaminate according to claim 1, wherein if first attenuated zones extendbeyond the corresponding bonded zone into a non-bonded zone of ply A,then at least 50% of a width of the adjacent non-bonded zone is notattenuated, this width being measured along a curvature thereof.
 13. Thelaminate according to claim 1, having only a single fluted ply A whereinthe flutes have a generally sinuous configuration with crests projectingon opposite sides of the central plane of the ply A and a single flatply B is laminated to the attenuated crests of fluted ply A on one sidethereof.
 14. The laminate according to claim 1, wherein the fluted ply Afurther includes second attenuated zones elongated in the direction ofthe flutes but having a narrower transverse dimension than that of thefirst attenuated zones including the bonded zones.
 15. The laminateaccording to claim 1, further comprising a second non-waved monofilm ormultifilm formed ply C comprising a thermoplastic polymer material,where the ply C is bonded to the crests of a second side of the ply,optionally through a lamination layer.
 16. A the laminate according toclaim 1, further comprising a second monofilm or multifilm formed ply Dcomprising a thermoplastic, cold-orientable polymer material, where theply D has a waved flute configuration and some of crests on a first sideof the ply D are bonded to a second side of ply B, optionally through alamination layer.
 17. The laminate according to claim 1, wherein thecrests of at least some of the flutes of the fluted ply A have flattenedregions at spaced apart intervals along the length thereof and arebonded to the ply B to form each of the flattened flutes into a row ofnarrow pockets closed at their ends.
 18. The laminate according to claim17, wherein at least a plurality of mutually adjacent flutes of thefluted ply A have the flattened regions at corresponding lengthwiselocations therealong to thereby form a series of transverse rows offlattened regions extending at least partially across the fluted ply.19. The laminate according to claim 1, wherein the bonding of the crestsof the ply A to the first side of the ply B takes place by means of atleast one lamination layer.
 20. The laminate according to claim 1,wherein the polymer material of all the plies comprises mainly apolyolefin.
 21. The laminate according to claim 1, wherein the the firstattenuated zones of the ply A have a minimum thickness of the the firstattenuated zones is less than 75% of a maximum thickness of the ply A inthe non-bonded zones of the ply A.
 22. The laminate according to claim1, wherein the the ply A has a main direction of orientation, extendinggenerally parallel to the longitudinal direction of the flutes and theply B has a main direction of orientation that make an angle to the maindirection of orientation of the ply A.
 23. The laminate according toclaim 15, wherein the plies B and C each has its own main direction oforientation and the plies B and C are arranged in the laminate so thatthe main direction of orientation of the ply B criss-crosses the maindirection of orientation of the ply C.
 24. The laminate according toclaim 23, wherein the ply A in its unoriented state exhibits acoefficient of elasticity which is less than a coefficients ofelasticity of the plies B and C in their unoriented states.
 25. Thelaminate according to claim 1, wherein the polymer material of the ply Aand its state of orientation are selected such that the averagecoefficient of elasticity thereof as measured in a non-bonded zone in adirection parallel to the flutes thereof is at least 700 Mpa.
 26. Thelaminate according to claim 1, wherein at least some of channels definedby the flutes of the ply A and the first side of the ply B bondedthereto contain a filling material selected from particles, fibers,filaments, and liquids.
 27. The laminate according to claim 26, whereinthe material is a preservative for goods intended to become packed in orprotected by the laminate selected from the group consisting of anoxygen scavenger or ethylene scavenger, a biocide, a corrosion inhibitorand a fire extinguishing agent.
 28. The laminate according to claim 27,wherein the channels include perforations established in the flutes ornon-waved film material to enhance the effect of the preservative. 29.The laminate according to claim 26, wherein the filling materialcomprises reinforcement strands.
 30. The bag made from a laminateaccording to claim 1 which is constituted of a single fluted ply A and asingle flat ply B bonded together in sheet-form, the bag having itsopposite side walls made of the sheet-form laminate and its top andbottom ends closed along lines generally perpendicular to the directionof the flutes of the laminate.
 31. The laminate according to claim 1,wherein the respective plies A and B on opposite sides of each of atleast some of the flutes are provided with a row of perforations whichon the opposite sides are displaced relative to one another whereby afluid material passing perpendicularly through the laminate is divertedfrom a straight path.
 32. The laminate according to claim 1, wherein awavelength of the flutes of the fluted ply A is no more than about 3 mm.33. The laminate according to claim 1, wherein a wavelength of theflutes of the fluted ply A is no more than about 2.5 mm.
 34. Thelaminate according to claim 1, wherein a wavelength of the flutes of thefluted ply A is no more than about 2.0 mm.
 35. The laminate according toclaim 1, wherein a wavelength of the flutes of the fluted ply A is nomore than about 1.5 mm.
 36. The laminate according to claim 1, whereinthickness limits of an attenuated zone is taken to be loci where the plythickness is an average between its minimum attenuated thickness and itsmaximum thickness in an adjacent non-attenuated zone.
 37. The laminateaccording to claim 24, wherein the flutes are flattened at intervals andbonded across each ones entire width to make the flute form a row ofnarrow closed pockets.
 38. The laminate according to claim 26, whereinthe filling material is adapted to act as a filter material by holdingback suspended particles from a liquid passing through the channels orpockets or is an absorbent or ion exchanger capable of absorbing orexchanging matter dissolved in such liquid, the filler optionallybeingfibre-formed or yarn-formed, and that each filled flute andmatching non-waved film material is supplied with a row of perforations,whereby the perforations or groups of perforations in a flute and theperforations or groups of perforations in the matching non-waved filmmaterial are mutually displaced so as to force the liquid with thesuspended particles, while passing from one surface of the laminatetowards the other surface, to run through the filter material in adirection parallel to the longitudinal directions of the flutes.
 39. Thelaminate according to claim 19, wherein the at least one laminationlayer is formed by extrusion during the bonding process.
 40. Thelaminate according to claim 19, wherein the ply A and the ply B includea coextruded lamination layer that bond ply A to ply B during thebonding process.
 41. A method for forming a polymeric laminate, whichcomprises the steps of: passing a ply A formed of monofilm or multifilmcomprising a solid-state orientable thermoplastic polymer material,while in a solid state, through a pair of grooved attenuating rollersadapted to subject the ply A to a generally lateral stretching toattenuate the ply A in a set of narrow elongated zones which arelaterally spaced apart to form first attenuated zones and non-attenuatedzoned in the ply A so that the ply A has a variable thickness, where athickness of first attenuated zones are less than a thickness of thenon-attenuated zone; in concert with the first passing step orsubsequent to the first passing step, passing the attenuated ply Abetween a pair of grooved rollers to produce a fluted ply A with crestsof flutes formed thereby on one side of the ply A generally coincidingwith the first attenuated zones; and passing the fluted ply A and a flatply B comprising a thermoplastic polymeric material in sandwichedrelation through a pair of laminating rollers of which at least one ofthe rollers is grooved under sufficient heat and pressure as toadhesively bond a first side of the ply B to crests of a first side ofthe ply A, where the grooves of the laminating roller are arranged ingeneral registration with the grooves of the attenuating and/or thefluting grooved rollers so that the bonding of the ply A to the ply Btakes place mainly within the attenuated zones.
 42. The method accordingto claim 41, including the step of before or after passage of the ply Athrough the grooved attenuating roller pair for lateral stretchingthereof, passing the fluted ply A through an additional pair ofattenuating grooved rollers adapted to subject the ply A to lateralstretching to attenuate the same in a second set of narrow elongatedattenuated zones which are parallel to the flute direction and laterallyspaced apart in alternating relation to the first set of attenuatedzones, the lateral dimension of the second set of attenuated zones beingless than that of the first set of attenuated zones.
 43. The methodaccording to claim 41, wherein a lateral spacing of the grooves of thelaminating grooved roller measured parallel to the roller axis is notgreater than 3.0 mm.
 44. The method according to claim 41, wherein theply A before the formation of the flutes is subjected to orientation sothat the ply A has a main direction of orientation which correspondswith the direction to be taken by the flutes.
 45. The method accordingto claim 41, further comprising the step of, simultaneously with orsubsequent to the bonding of the ply B to the ply A, bonding a secondnon-waved monofilm or multifilm formed ply C comprising a thermoplasticpolymer material to the crests of the ply A on a second side thereof.46. The method according to claim 41, wherein the plies A and B comprisemainly a polyolefin and are formed by an extrusion process.
 47. Themethod according to claim 41, wherein at least one of the plies includesa surface layer adapted to facilitate lamination of the ply while a bodyof the ply remains in its solid state.
 48. The method according to claim41, wherein after the lamination at least some of the resultant flutesare subjected along transverse loci at selected intervals along theirlength to heat and pressure that are sufficient to bond together theplies along such loci to thereby deform the flutes into rows of discretepockets.
 49. The method according to claim 48, wherein the heat andpressure to deform the flutes is applied by means of at least onelaterally extending bar or cog which extends over at least a pluralityof the flutes and is adapted to be brought into pressure contact withthe flutes at the selected intervals.
 50. The method according to claim41, wherein the first attenuated zones are given a distinctive stripecharacter either by heating the crests of the grooved roller of theattenuating roller pair which correspond to the first attenuated zonesto a higher temperature than the crests of its mating grooved roller orby selecting a lesser radius of curvature for the corresponding creststhan for the crests of the mating roller.
 51. The method according toclaim 41, comprising the further step not later than during thelamination of the plies, of introducing a particulate, liquid, orelongated thread material into at least some of the flutes which arecreated to form filled channels by the lamination.
 52. The methodaccording to claim 51, comprising the further step after the laminationof applying to discrete loci across at least some of the filled channelsat spaced intervals along the length thereof heat and pressuresufficient to close the filled channels at the loci with the materialtherein and thereby form filled pockets.
 53. The method according toclaim 51, comprising the further step of forming in the respective plieson opposite sides of at least some of the filled pocktes at least onerow of perforations which on the opposite sides are displaced out ofalignment relative to one another whereby a fluid material passingperpendicularly through the laminate is diverted from a straight path.54. The method according to claim 41, wherein prior to the lamination,the ply B is given an orientation generally transverse to the directionof the ultimately formed flutes, and comprising the further step ofsubjecting the ply B after the lamination to shrinkage in the generallytransverse direction.
 55. The method according to claim 41, wherein theply A is supplied with attenuated zones and flutes with the flutesextending in a direction essentially parallel to the length of ply A bypassing ply A through at least one set of driven mutually intermeshinggrooved rollers to transversely stretch the same, the grooves of therollers being either circular or helical along an angle of at least 60°to the roller axis.
 56. The method according to claim 55, comprising thefurther step of delivering the ply A after the same exits from one ofthe intermeshing grooved rollers directly to the grooved laminationroller, the two grooved rollers being in close proximity to one anotherand having the same pitch when measured at the operational temperaturesthereof.
 57. The method according to claim 55, comprising the furtherstep of after the ply A exits from one of the intermeshing groovedstretching rollers, passing the same over at least one grooved transferroller before delivery to the grooved lamination roller, all of therollers in the sequence having the same pitch when measured at theirrespective operating temperatures.
 58. The method according to claim 41,wherein each grooved roller used to form the flutes in ply A and tolaminate ply A to ply B and each arooved roller used to form theattenuated zones and the at least one grooved roller used in thelamination step are grooved rollers where the grooves of each groovedroller are essentially parallel to its axis.
 59. The method according toclaim 58, further comprising the step of directing a flow of air todirect the ply A into the grooves of one of the grooved flute-formingrollers.
 60. The method according to claim 41, wherein at least one ofthe plies A and B is provided with a laminating layer on a surfacefacing the other ply to facilitate in the lamination.
 61. A methodaccording to claim 41, further comprising the step of applying printedmatter on a surface of the ply A and/or B in registration with the theflute-forming and lamination processes so that the printing is on aninside of the laminate in non-bonded zones while the bonded zones aregenerally free of printed matter.
 62. The method according to claim 41,wherein the lateral spacing of the grooves of the laminating groovedroller measured parallel to the roller axis is not greater than 2.5 mm.63. The method according to claim 41, wherein the lateral spacing of thegrooves of the laminating grooved roller measured parallel to the rolleraxis is not greater than 2.0 mm.
 64. The method according to claim 41,wherein the lateral spacing of the grooves of the laminating groovedroller measured parallel to the roller axis is not greater than 1.5 mm.65. The method according to claim 41, wherein a groove configuration ofthe attenuating rollers is different from a groove configuration of thegrooved laminating rollers.
 66. The method according to claim 41,further comprising the step of producing, in that in a manner similar tothe forming and application of A, a second monofilm formed or multifilmforms ply (D) having waved flute configuration with a wavelengthpreferably of no more than 3 mm, and the crests on one side of D arelaminated to the second side of B simultaneously with or following thelamination of B with A.
 67. The method according to claim 51, furthercomprising the step of perforating, prior to, simultaneously with orfollowing the filling step, the laminate at least on one side to helpthe filling material or part thereof dissipate into the surroundings orto allow air or liquid to pass through the pack of filling material. 68.An apparatus for producing a laminate comprising a ply A and a ply B allformed of at least one monofilm or multifilm and comprising mainly athermoplastic polymer material, which apparatus comprises: a firstattenuation station for stretching the ply A in its solid state in adirection laterally of the flutes along laterally spaced lines to formlaterally spaced apart first attenuated zones of reduced thickness inthe ply A; combined with or downstream of the first attenuation station,a fluting station including a pair of grooved fluting rollers forimparting to the ply A passed therebetween a wavy fluted configurationwith crests of formed flutes on one side of the ply A generallycoinciding with the first attenuated zones; means for feeding acontinuous web of the ply A to the attenuating stations; and downstreamof the fluting station, at least one laminating station including a pairof laminating rollers of which at least one of the rollers is groovedfor laminating a first side of the ply B to the crests of some of theflutes of a first side of the ply A to form a laminate; means forapplying heat and pressure to the grooved laminating roller of thelaminating station and/or a counter-roller to the latter to form bondingzone between the ply A and the ply B, where the first attenuation zoneshave a width and alignment such that each of the bonding zones liesmainly within a first attenuation zone; and means for feeding acontinuous web of the ply B to the laminating station to form thebonding zones between the ply A and the ply B.
 69. The apparatusaccording to claim 68, wherein the intermeshing pair of grooved rollersin the fluting station also serve to stretch the ply A in its solidstate in a direction laterally of the ultimately formed flutes alonglaterally spaced lines to form the laterally spaced apart firstattenuated zones of reduced thickness in the ply A, the grooves of thegrooved roller pair and the grooved laminating roller being so alignedthat each of the bonding zones lies mainly within a first attenuatedzone.
 70. The apparatus according to claim 68, wherein the attenuationstation comprises upstream of the pair of fluting rollers, at least onepair of intermeshing grooved stretching rollers for stretching the ply Ain its solid state in the lateral direction, the grooves of thestretching rollers and the grooved laminating roller being so alignedthat each of the bonding zones lie mainly within the first attenuatedzones and the feeding means for ply A first feeds the ply A to the pairof intermeshing grooved stretching rollers.
 71. The apparatus accordingto claim 68, further comprising heating means for heating the ply A indiscrete zones corresponding to the ultimately formed first attenuatedzones and thereby facilitate the attenuation.
 72. The apparatusaccording to claim 71, wherein the heating means comprises upstream ofthe lateral stretching grooved rollers for making the first attenuatedzones a heated grooved roller having heated tips of the grooves thereofin contact with one side of the ply A in line with the grooves of theattenuation rollers.
 73. The apparatus according to claim 72, whereinthe radius of curvature of the tips of at least one of the stretchingrollers, the radius of curvature of the tips of the heated groovedroller and the temperature of the latter, the speed of travel of the plyA through the stretching rollers, and the degree of intermeshing of thegrooved attenuation rollers are selected to achieve an attenuation ofthe ply A in the first attenuate zones reducing the thickness thereof bymore than 25%.
 74. The apparatus according to claim 68, wherein thecrests of the grooved laminating roller are flat and have a dimensionmeasured along the roller axis in the range of 0.15–0.90 times adivision between crests of the grooved laminating roller.
 75. Theapparatus according to claim 68, wherein the laminating stationcomprises a flat roller having rubbery surfaces and the grooved rollerof the laminating station is adapted to apply heat and pressure to theplies fed between the rollers.
 76. The apparatus according to claim 68,further comprising at least one grooved transfer roller arranged betweenthe grooved rollers of the fluting station and the grooved roller of thelaminating station such that the ply A is maintained generally incontact with the surface of at least one grooved roller from itsentrance into the grooved rollers of the fluting station to it exit formthe grooved roller of the laminating station.
 77. The apparatusaccording to claim 68, wherein the grooves of all the grooved rollersare circular.
 78. The apparatus according to claim 68, wherein thegrooves of all the grooved rollers extend parallel to the axes of therollers.
 79. The apparatus according to claim 68, further comprising: aprinting station at least prior to the lamination station for applyingto a surfaces of the ply A and/or ply B printed matter, where theprinted matter is applied in registration with the non-bonded zones ofthe ultimate laminate leaving the bonded zones generally free of suchmatter.
 80. The apparatus according to claim 68, further comprising:downstream of the lamination station a flute flattening station forapplying pressure across at least some of the flutes of the laminate ofthe plies at localized loci spaced intermittently along the length ofthe flutes and means for delivering the laminate from the laminationstation to the flute flattening station.
 81. The apparatus according toclaim 68, further comprising: downstream of the lamination stationperforating means for perforating the plies of the resultant laminate inthe non-bonded zones thereof.
 82. The apparatus according to claim 68,further comprising intermediate the fluting station and the laminationstation a filling station for introducing filling material into theinterior of the flutes for incorporation into the laminate produced bythe lamination station.
 83. The apparatus according to claim 68, whereina division between crests of the grooved laminating roller is notgreater than about 3 mm.
 84. The apparatus according to claim 68,wherein a division between crests of the grooved laminating roller isnot greater than about 2.5 mm.
 85. The apparatus according to claim 68,wherein a division between crests of the grooved laminating roller isnot greater than about 2.0mm.
 86. The apparatus according to claim 68,wherein wherein a division between crests of the grooved laminatingroller is not greater than about 1.5 mm.
 87. The apparatus according toclaim 68, further comprising second attenuating station including asecond pair of intermeshing grooved stretching rollers for solid-statestretching of the ply A in a direction substantially perpendicular tothe flutes upstream of the laminating roller, to form second attenuatedzones mutually separated in the perpendicular direction, the grooves ofthe second stretching rollers being adapted and aligned relative to thegrooves of the laminating roller so that the second attenuated zones arelocated between the first attenuated zones whereby a second attenuatedzone is located between each adjacent pair of first attenuated zones.88. The apparatus according to 68, further comprising: means forsupplying the laminate from the laminating station to a downstream C plylaminating station; means for supplying a continuous web ofsubstantially smooth ply C formed of a thermoplastic material from asupply to a second laminating station so as to be in face to facerelationship with the A/B laminate and in contact with the second sideof the ply A, where the second laminating station comprises rollers forapplying mild pressure between the ply C and the A/B laminate to bondsome of the crests of the second side of the ply A to a first side ofthe ply C without flattening the flutes of the ply A.
 89. The apparatusaccording to 88, further comprising: means for heating the surface ofthe second side of the ply A of the A/B laminate and/or the face thefirst side of the ply C brought into contact with the A/B laminate priorto or simultaneously with application of mild pressure in the secondlaminating station.
 90. The apparatus according to 68, furthercomprising: a second fluting station including a grooved ply D flutingroller for imposing a waved fluted structure on a ply D comprising athermoplastic material; feeding means for feeding a continuous web ofthe ply D formed of the thermoplastic material from a supply to thesecond fluting station; a second laminating station comprising a groovedply D laminating roller for applying heat and pressure between one sideof the ply D and the second side of the ply B of the A/B laminate toform bonding zones between some of the crests of this side of the ply Dand the second side of ply B in the A/B laminate; and means forsupplying ply A/B laminate or the plies A and B to the second laminatingstation.